1. Field of the Invention
The present invention relates to a golf club and more particularly to an improvement in the structure for attaching the ferrule to the club shaft.
2. Prior Art
In golf clubs such as irons and woods as shown in FIG. 3, the tip-end e of the club shaft d is inserted and bonded via a bonding agent P in a club shaft insertion hole c formed in the hosel b of the club head a. A ferrule member f made of a plastic such as Celluloid (trademark) is installed in the opening end of the club shaft insertion hole c which constitutes the boundary base part of the joint area between the hosel b and the tip-end e of the club shaft d.
Due to the use of the ferrule member f, the golf clubs can prevent the local concentration of stress that is caused by the shock of hitting the ball in the boundary base part in the joint area between the hosel b and the tip-end e of the club shaft d. The ferrule member f can also enhance a cosmetic effect in terms of the external appearance of the golf club.
When the ferrule member f is mounted in the joint area between the hosel b of the club head a and the tip-end e of the club shaft d, the ferrule member f is first fitted in the opening end of the club shaft insertion hole c of the hosel b, and then the tip-end e of the club shaft d is pressure-inserted into the through-hole g. The tip-end e of the club shaft d has an outer diameter that is 0.1 to 0.5 mm greater than the hole diameter of the through-hole g of the ferrule member f so as to obtain a tight fitting between the two.
In other words, the club shaft d is forcibly inserted into the ferrule member f and the ferrule member f is retained on the club shaft d by the pressing force that is obtained from the contraction of the ferrule member f. Thus, the ferrule member f is retained on the club shaft d by means of the so-called "caulking." Accordingly, as shown in FIG. 4, the ferrule member f would slip out of the club shaft insertion hole c of the hosel b and slide away from the hosel b in the axial direction of the club shaft d as indicated by arrow X as a result of the shock of striking the ball during long-term use of the golf club. As a result of such "floating" of the ferrule member f, a local stress concentration occurs in the boundary base part of the joint area between the hosel b and the club shaft d; and, the club shaft d easily breaks.